American Staf·ford·shire terrier 
(stăfərd-shîr′, -shər)
(stăfərd-shîr′, -shər)n.
A dog of a medium-sized breed developed from the American pit bull terrier, having a muscular body, broad head with powerful jaws, short stiff coat, and black nose. It is often referred to as a pit bull.
[After the STAFFORDSHIRE BULL TERRIER, the breed from which the American Staffordshire terrier was developed.]